3.5 $ P.I.R. Arduino Intruder Alarm

Introduction: 3.5 $ P.I.R. Arduino Intruder Alarm

Passive infrared sensors are great for motion detection projects, i brought it recently for a college project and i was actually being tempted to use it .Unfortunately all i got from The INTERNET were not that much fun .I took out some of my favorite old parts and started tinkering with it .

The result was a motion detected Intruder alarm.I added two led to simulated police siren light and added Siren to it for the real fun.The sensitivity was made to medium values , and then the fun began .

Note this might look like an egg according to my Girl Friend dont try to boil it and eat it :P

Step 2: About the PIR Sensor

PIRs are basically made of a pyroelectric sensor.The one above as the round metal can with a rectangular crystal in the center.It can detect levels of infrared radiation. Everything emits some low level radiation, and the hotter something is, the more radiation is emitted. The sensor in a motion detector is actually split in two halves. The reason for that is that we are looking to detect motion (change) not average IR levels. The two halves are wired up so that they cancel each other out. If one half sees more or less IR radiation than the other, the output will swing high or low.

There are two Trimmer in the PIR sensor this pots adjust the delay time and the sensitivity ,individually i added the note in the 3rd pic for references.

There is also a jumper for selecting the trigger mode ,

There are two trigger modes

H (re trigger ):Output remains high when sensor is triggered repeatedly and low when idle.